Field of the Invention
The invention relates to a method for applying a protective film of, for example, oil to the interior of a metal pipe for preservation purposes. The invention furthermore relates to apparatus for applying a protective film of, for example, oil to the interior of a metal pipe for preservation purposes, at least comprising a storage vessel for, for example, oil.
Metal pipes are commonly known semi-finished products, which are manufactured in various lengths, wall thicknesses and diameters. In the process industry and in the installation industry, for example, it is very desirable that the interior of such semi-finished pipes are clean and non-corroded. Usually such pipes are provided with a protective film of oil for interim storage and transport to the end user, which oil film, due to its preserving action, prevents corrosion on the inside of the pipe. A known method for applying an oil film to the interior of a metal pipe is to submerge such a pipe in an oil bath. This method requires a great deal of time and space, however, whilst it is furthermore characterized by excessive oil consumption, which burdens the environment, and said method is not very efficient and functional when pipes of considerable length are to be preserved. In addition, said method is not suitable for use with pipes having a small diameter, since the oil cannot penetrate into the pipe sufficiently well upon submersion. Moreover, it is practically impossible to remove the (excess) oil after the treatment.
A prior arrangement consists of moving an oil-soaked wad through the pipe, which wad is connected to a rod which is moved forward and backward through the pipe. Moving the rod with the oil-soaked wad through the pipe is a laborious and time-consuming activity, which makes the apparatus unsuitable for preserving pipes having a considerable length or a small diameter. In addition, there is a risk of the wad remaining behind in the pipe after the treatment and obstructing said pipe, as a result of which the pipe will be unusable.
Further drawbacks of the known methods and apparatus are the fact that they can only be used with straight pipes and that it is difficult to ascertain after each treatment whether the interior of the pipe is fully coated with an oil film.